Synergistic approach to colloidal stability and thermophysical optimisation of multiwalled carbon nanotubes, aluminium nitride, and silver-based hybrid nanofluids

Hybrid nanofluids are transforming the field of thermal management by significantly enhancing heat transfer efficiency through the synergistic interactions of different nanoparticles. This study meticulously investigates the effect of volumetric ratios and surfactant effects on the colloidal stability, heat transfer characteristics, and costeffectiveness of hybrid and tri-hybrid nanofluids comprising multi-walled carbon nanotubes (MWCNTs), silver (Ag), and aluminium nitride (AlN). Various formulations were prepared with different volumetric ratios and analysed over a temperature range of 20 to 45 °C. Experimental results revealed that SDBS consistently outperformed the others, by maintaining a stable suspension and thus preserving the enhanced thermal properties over extended periods. It was found that, among the nanofluids investigated, MWCNTs exhibited the highest thermal conductivity enhancement of 8.57%. The trihybrid nanofluid with a 20/60/20 MWCNTs/Ag/AlN ratio achieved a comparable enhancement of 8.14%, demonstrating that optimized nanoparticle combinations can provide excellent thermal properties, stability, and cost-efficiency. However, this
trihybrid formulation also showed the highest viscosity increase noted to be 5.55%, compared to a 4.43% increase for simple Ag nanofluids. Additionally, the highest density increase was 0.25% for Ag nanofluid while among hybrid formulations the maximum was 0.22% % observed for 80/20 Ag/AlN. Cost analysis indicated that the trihybrid nanofluid with a 20/40/40 ratio is the most cost-effective option when cost considerations are as important as thermal performance. However, for applications where maximising thermal performance is crucial, the tri-hybrid with a 20/60/20 ratio is the preferred choice.